1. Field of the Invention
The present invention relates to a sealing device for sealing an outer periphery of a rotating body, and more particularly to a sealing device provided with a pulsar ring of a rotary encoder for detecting a rotation.
2. Description of the Conventional Art
FIG. 8 is a cross sectional view showing a sealing device for sealing a bearing portion of a wheel suspension device for a motor vehicle by cutting it along a plane passing through an axis O. This kind of sealing device 100 is also called as a hub seal, and is structured to be installed between an outer ring 201 and an inner ring 202 of a bearing 200 in order to prevent muddy water or the like from making an intrusion into a bearing inner portion B from a bearing outer portion A.
In particular, the sealing device 100 shown in FIG. 8 is provided with a metal installation ring 101 pressure-inserted and fitted to an inner peripheral surface of the outer ring 201 of the bearing 200, and a side lip 102 and a radial lip 103 integrally provided on the installation ring 101, and the side lip 102 and the radial lip 103 are slidably brought into close contact with a slinger 104 tightly fitted to an outer peripheral surface of the inner ring 202. Describing in detail, the side lip 102 and the radial lip 103 are made of a rubber-like elastic material, and are integrally bonded by vulcanization to the installation ring 101 via a common base portion 106. The side lip 102 is slidably brought into close contact with an inner side surface of a seal flange portion 104a of the slinger 104 by its tip end, and the radial lip 103 at an inner peripheral side thereof is slidably brought into close contact with an outer peripheral surface of a sleeve 104b of the slinger 104 by an inner peripheral edge of its tip end directed to an outer side.
In this case, this kind of sealing device 100 includes a sealing device provided with a rotary encoder for detecting a rotating speed and an angle of rotation of a shaft in addition, and a structure, for example, disclosed in-Japanese Unexamined Patent Publication No. 2004-93554 has been conventionally known as a typical example. FIG. 9 is a cross sectional view showing the same kind of conventional sealing device with the encoder as the in Japanese Unexamined Patent Publication No. 2004-93554 by cutting it along a plane passing through an axis O.
In particular, the sealing device with the encoder disclosed in the patent document 1 is structured such that, as shown in FIG. 9, a pulsar ring 105, which is formed by a magnetic rubber and is magnetized to be multipolar at a predetermined pitch in a circumferential direction, is integrally provided on an outer surface of the seal flange portion 104a of the slinger 104 in the sealing device 100 having the specification shown in FIG. 8. In this case, the magnetic rubber is obtained by mixing a magnetic body into a rubber-like elastic material. Further, a magnetic sensor 120 is arranged at an outer side of the pulsar ring 105 so as to oppose thereto in a non-rotating state, and the magnetic sensor 120 constructs the rotary encoder together with the pulsar ring 105, and generates a pulse having a waveform corresponding to a change of a magnetic field caused by rotation of the pulsar ring 105 together with the inner ring 202 of the bearing 200 so as to detect the rotation.
However, it is an actual condition that the pulsar ring 105 for constructing the magnetic type rotary encoder is conventionally applied only to the slinger 104 of the sealing device 100, as shown in FIG. 9.